Studies of muscle morphology including determination of muscle fiber types and muscle capillary density in patients with lipodystrophy will be accomplished in order to gain an understanding aspects of insulin resistance in congenital lipodystrophy. Muscle volume will be quantified by magnetic resonance imaging of the whole body and the presence of fat in peritoneal and retroperitoneal distribution will be determined. Abnormalities in muscle energy metabolism will be determined by 31P nuclear magnetic spectroscopy.